Chromatic dispersion is caused by material dispersion, resulting from variation in the refractive index of an optical material, and waveguide dispersion, resulting from changes in the distribution of light between the core and the cladding of a single mode fiber. Accurate measurement of chromatic dispersion in optical transmission networks is of paramount importance to enable proper compensation. Chromatic dispersion results in different propagation speeds for optical signals of different wavelengths, which in turn causes temporal spread of optical signals and limits the reach of an optical link and the data rate carried by a wavelength channel within the link. Therefore, determining and compensating chromatic dispersion are necessary for realizing large-scale wide-coverage optical networks supporting data streams of high bit rates.
Traditional methods of compensating for chromatic dispersion include measuring individual fiber spans in an optical network using external dispersion measurement equipment and applying pre-defined and granular dispersion compensation devices at pre-determined points in the optical network. Such methods usually require a high-speed external modulator and external access to a fiber span under test in order to perform the chromatic-dispersion measurement, and are therefore inefficient, intrusive and labor intensive.
Therefore, there is a need for developing alternative methods and systems for measuring and compensating chromatic dispersion which aim at avoiding or mitigating the above-mentioned drawbacks.